Automatic tuning for radio receiving apparatus



Oct 15, 19 Q- A. HQROWITZ ET AL 2,218,083

AUTOMATId 'rumne FOR mmo kncmvme APPARATUS Filed Oct. 4, 193a 2 srshe'et1 INVENTORS A. HOROWITZ G. B. KNOS i A 0R EY Oct. 15, 1 A. HOROWITZ ETAL AUTOMATIC TUNING FOR RADIO RECEIVING APPARATUS Filed Oct. 4, 1938 2Sheets-Sheet 2 SW8 WY mwo 4% N .0 w wmm m 7 A Patented a. 15, 1940AUTOMATIC TUNING FOR RADIO RECEIV- ING APPARATUS Alexamlre Horowitz andGunnar Borge Knos, Eindhoven, Netherlands, asslgnors, by memoassignments, to Radio Corporation of America, New York, N. Y, acorporation of Delaware Application October 4, 1938, Serial No. 233,18

In Germany March 18, 1938 I Claims. (Cl. 172-239) Radio receivingapparatus adapted to be automatically tuned to a plurality ofpre-determined stations with the aid of a station selector' conslstingof a selector disc, a key-board or asimilar '5 device are already known.In such apparatus there is for each of these stations apositiondetermining disc which is coupled with the shaft of the tuningcondenser and which is equipped with two guide tracks which difl'er inoperative height and with which cooperates a member for the motor bywhich the tuning members are ad- Justed. In these known apparatus thepositiondetermining disc consists as a rule of a flat disc provided atits circumference with two circular guide tracks which, having differentdiameters are also different in operative height. By the operativeheight" of the guide tracks we mean hereinafter the height of theoperative guide portions with respect to a fixed plane. In the known 50devices these position-determining discs are mounted on the shaft of themovable portion of the tuning condenser. Owing to the manipulation ofatuning member, for example, a pushbutton corresponding to one of thestations which are to be automatically tuned, an actuating member forthe motor which actuates the tuning members, in the present instance therotor of the tuning condenser, comes into contact with one of bothportions of the guide track with the result, that the motor startsrotating and continues to rotate until the actuating member for themotor attains the point where the one guide track merges into the othertrack on the position disc under consideration. By. exactly adjustingthe position-determining discs'on the shaft of the tuning condenser itis achieved that at the moment whenv the actuating member is at thepoint where the one guide track merges into the other, correct tuning ofthe condenser is obtained.

- The invention relates to'a radio receiving apparatus of theabove-described kind, wherein, however, owing to the particular shape ofthe guide tracks, it is achieved that automatic tuning is effected withconsiderably greater precision than in the known devices. The apparatusaccording to the invention is characterised in that each of the twoguide tracks with different operative heights which are provided on theposition-determining discs which are driven at a higher speed than theshaft of the. condenser devices. The transmission between the shaft ofthe position-determining disc and the shaft of the movable condenserportion must be chosen in proportion to the length of each of the guidetracks. 5

In one particular form of construction of the apparatus according to theinvention the guide tracks are provided in the form of helical lines onthe cylindrical outer surface of the positiondetermining discs.

In a further embodiment the guide tracks are provided in the form ofspirals on one of the, preferably flat, terminal faces of the disc.

In the first-mentioned case the discs are consequently formed more orless as drums and the shaft on which the discs are mounted is preferablyhorizontally disposed.

In the second form of construction the position discs may be formed asgramophone records, in the sense that in this case'the groove usuallypresent in such a record has two diiferentproflles, for example, depths.The shaft of the discs is preferably arranged in this case so as tooccupy a vertical position.

Owing to the fact that the guide tracks extend 2 over an angle whichexceeds an angle of having its apex inthe centre line of the shaft andconsequently have, in the forms of construction' shown, the shape ofhelices of spirals, the path traversed, in the manipulation of a stationselector by the actuating members for the motor by which the,tuningmembers are adjusted, is V considerably longer than in the knowndevices. Slight inaccuracies which may be due, for example, to theunavoidable inertia of the rotor' of 35 the motor, consequently havesubstantially no influence on the correct tuning and the forces by whichthis is brought about may be considerably smaller. Furthermore theamount of play which is always present is, also considerably 40 smaller.In order to ensure that the angle of rotation of theposition-determining discs should correspond to the materially smallerangle of rotation ofthe movable portion of the tuning condenser, theshaft on which the discs are 45 mounted must be driven at an increasedspeed with respect to the shaft of the tuning condenser.

The manner in' which the two guide tracks with diflerent operativeheights provided on each of the position discs merge into one anothermust 5, be chosen inaccordance with ,the method by i which automatictuning is affected in one system i I these two guide tracks on each ofthe position discs are separated, in accordance with the invention, by adepression which has at its base it tracks.

According to the invention, in a further system the two guide tracks oneach position disc are separated by a portion which gradually passesfrom the operative height of the oneguide track to that of the other.

In a further system according to the invention the two guide tracks oneach position disc are separated by a contact surface which makes anangle of 90 or less with the guide track of larger operative height.

It is evident that the guide tracks may have different forms. They maybe formed, for example, by grooves in the surface of the position discs.According to the invention it is alternatively possible to constitutethem by ridges on the position discs which are separated from oneanother by depressions.

The invention will be explained more fully with reference to theaccompanying drawings, wherein Fig. l discloses the automatic controlmechanism associated with the tuning element of a radio receiveraccording to the invention; Figs. 2 and 3 are views in cross-section andperspective respectively of one of the tuning elementposition-determining discs; Fig. 4 discloses in diagrammatic fashion thecooperation of the motor control switch, one of the push button mem--bers and its associated disc; Figs. 5-7 are modifled forms ofposition-determining discs that may be employed; and Fig. 8 is across-sectional viewof the form shown in Fig. 7.

Referring now to Fig. l the'tuning element of the radio receiver isrepresented by the usual tuning condenser, the rotor 2 of which ismounted on a shaft I which supports, in addition, a gear wheel 4 whichmeshes with a pinion 3. The pinion 3 is mounted on a shaft 5 whichcarries at one end a tuning knob 5 and at the other end the rotor of atuning motor 1. In this case the shaft 5 has mounted thereon fourposition-determining discs 8, 9, I and II which are formed as drums andon which helical guide tracks are provided. It may be noted that each ofthese discs co-operates with an actuating member (I2, I3, I4 and I) forthe tuning motor 1. These actuating members are mounted on arms I6, I1,I8 and i9 (shown in perspective) which are adapted to rotate aboutspindles 20, 2|, 22 and 23. This construction makes it possible for themembers actuating the motor to perform, when the shaft 5 rotates, areciprocating motion as is shown in Fig. 1 for the member I2, saidmotion being required to be enabled to follow the course of the helicalgrooves'24, 25, 25 and 21 in the position discs 8, 9, I0 and N.

Fig. 2 represents in transverse section the position disc 8 which isconstituted here by a moulding. This disc is mounted by a hub 23 on theshaft 5 and the drumlike outer surface has two helical guide trackswhich have different operative heights (hi larger than hz) The guidetrack of larger operative height hl is denoted by 29 and the guide trackwith the smaller operative height 112 is designated by 30.

Fig. 3 represents a perspective view of the disc 8, the situation of thehelical guide tracks on the drum-like surface of the disc 3 may beclearly seen from this figure.

As appears from Fig. 4, which shows diagrammatically the operation ofone of the tuning-systems, the guide track 29 with 'the larger operativeheight hl merges into the guide track 39 with the 1 smaller operativeheight hz through a depression a smaller operative height than the twoguide The base of this depression has a smaller operative height thanhave the guide tracks 29 and 30. A lever 33 carrying at its end a feeler34 whose lower end rests upon manipulation of a push-button 35, on thebase of one of the guide tracks 29 and 30, is pivoted on a point 52. Thelever 33 has an extension 36 which is provided at its upper end with aprojection 31. The push-button 35 is provided on a lever 39 which ispivoted on a point 39; it may be noted that between the levers 38 and 33there is provided a blade spring 40 which, when the push-button 35 isdepressed, exerts on the lever 33 a pressure which is directeddownwardly. The lever 33 is furthermore provided with an extension 4|which .has at its upper end a projection 42.

There are furthermore three contact springs 43, 44 and 45, which areprovided with contacts 46, 41 and 43. The projections 31 and 42 enterbetween the contact springs 43, 44 and 45. The contact spring 43 isformed in such manner that it always tends to move, as is shown, in thedirection of the arrow 1:, that is to say downwardly, whereas thecontact spring 45 always has a tendency to move upwardly, as isindicated by the arrow 1/. The contact springs 43 and 45 have eachconnected thereto a current supply conductor 43' and 45' respectively.The stator of the motor is provided with two oppositely wound windings43" and 45'. which are connected to the contact springs 43 and 45through their 'respective supply conductors 43' and 45. A

source of power supply S is connected between the current supplyconductor 44' of the contact spring 44 and the conductor connecting thetwo motor windings. It is consequently clear that when the contacts 45and 41 come into contact with one another, the motor starts rotating inthe one direction and, when the contacts 41 and 43 engage one another,the motor will rotatein the other direction.

If in the position shown the push-button 35 is depressed a projection 49provided on the lever 33 comes into contact with the lever 33, and ifthe push-button 35 is depressed still further the lower end of thefeeder 34 comes to rest on the base of the guide track 30. When thebutton 35 is beingdepressed the extensions and 4| also move downwardly.The projection 42, which initially prevented the contact 45 from cominginto contact with the contact 41 has also moved downwardly, just as theextensions 35 and 31. The projection 42 presses the contacts 41 and 43against one another with the result that the motor is energized by thewinding 45" whose circult is closed via the contacts 41 and 43. Thisresults in the right handed rotation of the motor. which lasts until theblade spring 40, by which the feeler 34 is depressed, acquires theopportunityof pressing said feeler into the depression 3| by which theguide tracks 29 and" are separated from one another. Owing to themovement which is now performed by the lever 33' the extension 35removes the lever 45 from the lever 44 with the result that the contact41, 43 is broken and consequently the motor is stopped. Any inertia ofthe motor has practically no in-. fluence on the tuning since, asappears from Fig. 1, the shaft 5 on which the position discs are mountedrotates at a higher speed than the shaft of the rotor 2 of thecondenser.

If the push-button had been depressed at the moment when the feeler 34was opposite the guide track 29 with the operative height hi, the feeler34 could be depressed only over a smaller distance than in thefirst-described instance. In consequence thereof the projection 42 wouldhaveallowed the lever 66 to move downwardly with'the result that thecontacts 66 and 61 would have come into contact with one another and themotor now energized by the winding 66" would have From Fig, 4 it mayfurthermore be seen that the lever 66 can pivot, in a planeperpendicular to the 291 plane of the drawing, on the spindle 66 whichis f sirnilar to the spindles 26, 2|, 2! and 26 of Fig. 1.

Fig. 5 represents one embodiment of the position disc in aradioreceiving apparatus according to the invention, wherein two helicalguide tracks SI and 62, whose portions shown in the figure arerepresented for simplicity as being located in one height he of theportion 6| into the operative height h1.0f the portion 62. At'the' point54 is pivoted a lever 65 whose finger 66 provided. at the end thereofbears permanently on one of the guide tracks 52 and Si so that the saidfinger always follows the course of the guide tracks. .The lever 66 isconnected by means of a conductor 61 to one of the terminals of themotor, which actuates the tuning means, said motor not being shown. Thislever carries a contact 66. Above and below the lever 66 there areprovided contacts 69 and 66. Depending on the fact whether the contact66 makes contact with the contact 59 or 66, which contacts are connectedby means of conductors 6| and 62 to two oppositely wound windings of themotor, the motor rotates lefthandedly or right-handedly until the finger66 attains the transition 66 between the two guide tracks, owing towhich the contact 66 is connected neither to the contact 66 nor to thecontact 66, so that the motor energizing circuit is broken and thetuning condenser remains in this position.

In the form of construction shown in Fig. 6 the two helical guide tracks66 and 66, whoseportions shown in Fig. 6 are represented for simplicity,as in Fig. 5, as located in a single plane, are separated by a contactsurface 66 which makes in this instance an angle a of 90 with the track66. If desired, this angle a may have a smaller value. On the guidetrack It bears the arm 66 of an angle lever which'ispivoted on a point61 and which is suspended from a slightly resilient lever 66. The lever66 is provided with a contact 66 which makes contact in this instancewith a resilient'contact III which has secured thereto a winding H ofthe motor for the tuning means 12, which motor is not shown. Below thelever 68 there is arranged a further lever 12 provided with a contact13. This lever has secured thereto a winding 16 of the motor which isoppositely'wound with respect to the winding II. The lever 66 isconnected by a wire 16 to the other terminal of the motor.

In the position shown the angle lever 66 raises the lever 66, owing tothe fact that the angle lever rests on the guide track", with the resultthat the contact 66 engages the contact 16 and the motor and thereforethe position disc shown start rotating in right-handed direction. At agiven instant the angle lever drops from the guide track 66 on the track66 with the result that the contact 66 engages the.contact '|6 and thesense of rotation of the motor is reversed, which motor consequentlystarts rotating in left-handed direction. This goes on until the arm 66of the angle lever butts against the contact surface 66 owing to whichthe angle lever rotatesiin the direction of the arrow and the arm 16 ofthe angle lever removes the lever if from the region of actionof thecontact 66 with the result that the motor energizing circuit is brokenand the shaft of the condenser comes to a stop.

Fig. 7 represents a form of construction of a position disc wherein theguide tracks are provided in the form of spirals on the flat terminalface ofthe position disc. In this form of construction a position disc11 is mounted on a shaft 16: the guide track with the larger operativeheight extends from A to B and that with the smaller operative heightfrom B to C. The transition from the one guide track into the other islocated at the point B; this transition may be formed in any tion-theguide tracks are formed by ridges l6 and 66 of the larger and. smalleroperative height, respectively, the ridges being separated from oneanother by depressions 6|. The grooves are hereassumed toextendhelically on the cylindrical drum-like surface of the position disc. Onthe top of the ridges rests an actuating member 62 of .the motor, whichmember is formed in this instance as a strap and is secured to a lever66 which, being pivoted on a point 64, is enabled to follow the courseof the guide tracks.

' What we claim is:

1. Mechanism for automatically adjusting a shaft to a plurality ofpredetermined positions, comprising a reversible motor for driving saidshaft, a plurality of shaft position-determining discs also driven bysaid motor, there being one such disc for each of the predeterminedshaft positions, each disc being provided with two guide tracks whichextend over an angle greater than 180 and which are spaced at differentradial distances from the shaft supporting the discs, switch' mechanismfor'controlling the direction of motor operation having a plurality ofcontrol members each cooperating with the guide tracks of one of thediscs, and manuallyoperated means for causing the selective cooperationof a particular control member with the guide tracks of its associateddisc whereby the motor is actuated to operate in the proper directionfor adjusting the shaft to the predetermined position.

2. Mechanism as defined in claim 1 wherein each of theposition-determining discs is in the form of a drum and the guide tracksare formed of said drum.

4. Mechanism as defined in claim 1 wherein each of theposition-determining discs is in the form of a flat disc and the guidetracks are in the form of spirals formed on the fiat surface graduallymerges from the operative height or of the disc. one guide track intothat of the other.

5. Mechanism as defined in claim 1 wherein 7. Mechanism as defined inclaim 1 wherein the two guide tracks on each position-deterthe two guidetracks on each disc are separated 5 mining disc are separated by adepression which by a contact surface which makes an angle of 5 extendsradially below the depth of the two approximately 90 with the guidetrack having guide tracks. the larger operative height.

6. Mechanism as defined in'claim 1 wherein the two guide tracks on eachposition-deter- ALEXANDRE HOROWITZ.

10 mining disc are separated by a portion which GUNNAR BORGE KNOS. 10

